138 MEDICAL ENTOMOLOGY 



and is transversely striated. At the base of each tube, where it joins 

 the oviduct, there is a peculiar funnel-shaped collar of thick chitin, 

 surrounded by a series of spiral filaments like the rings of a trachea. 

 The whole tube has a distinct coating of muscle fibres. In Phlebotom-us 

 there are only two spermathecae, one on each side of the middle 

 line at the junction of the oviducts. They are relatively large and 

 thin walled, but at the point where the duct leaves them the wall is 

 thicker, and is thrown into transverse ridges. In Musca (fig. 3) 

 there are three spermathecae resembling those of the mosquito, but 

 flattened at the top, and without a continuous chitinous wall. 



The accessory glands differ in size. In Anopheles they are very 

 small, and open near the lower end of the oviduct. In Tabanus (fig. 



5) they are large, and are conspicuous in dissections on 

 Accessory glands 



account of the dirty yellow colour of the secretion 



which they contain. The wall is composed of columnar epithelial 

 cells with many muscular fibres, and is thrown into longitudinal folds. 

 In Phlebotomus also there is a pair of long tubular glands. In Musca 

 (fig. 3) there are two pairs, one long and thin, and another, the so- 

 called conglobate gland, rounded or pear-shaped ; the latter is situated 

 close to the wall of the oviduct, and is often difficult to see on that 

 account. 



The pupiparous habit occurs in three distinct degrees in the Diptera. 

 In many Tachinids, which are not blood-suckers, the larvae are de- 

 livered almost as soon as they hatch out of the egg, 

 The Reproductive and are y sma ll. They undergo little or no develop- 

 Organs in the Pupi- . , " 



parous Flies ment in the uterus, and are laid in a large batch, exactly 



as eggs are laid. If the ovaries are dissected out just 

 previous to oviposition the young larvae can be seen within the egg 

 membranes ; they are perfectly formed and show active movements, as if 

 they were trying to find a way out of the egg. In the next degree, which 

 is instanced by two species of Musca, namely, corvina, Fabr., var. 

 vivipara Portschinski, and bezzii, Patton and Cragg, which are both 

 blood-feeders, the larva is retained and nourished for a part of its 

 life in the genital tract of the female, but is deposited while still young, 

 and completes its growth under conditions similar to those of its allies. 

 In the third degree the larva is retained until it is ready to pupate, 

 and in consequence of its large size during the later stages the genital 

 tract is greatly altered in its shape and relations. Glands are also deve- 

 loped to provide nourishment for the growing larva. 



As the Tachinidae are not blood-feeders they need not be discussed 



